The greenhouse effect caused by excessive use of fossil fuels has become a serious problem. In order to solve this problem, research into alternative energies is ongoing. Representative examples of alternative energy are wind power, wave power, and solar energy.
Recently, technology for power generation using solar energy has become competitive due to a dissemination of technology related to renewable energy, a decrease in solar cell cost, etc. In addition, the technology is being standardized. FIG. 1 is a view showing an example of a photovoltaic (PV) system disclosed in Korea Patent Application Publication No. 10-2000-0002864. As shown in FIG. 1, each of solar (or photovoltaic) modules (or panels) a, . . . , c, d, e includes a plurality of solar cells a1, . . . , e1, . . . , and a communication device 4. A central server 5, which is far from the solar modules, controls, maintains, and monitors the solar modules through the communication device 4.
However, it is difficult to check solar module faults (short-circuit, disconnection, etc.) by naked eye. Also, the faults rarely occur in newly established systems. Furthermore, in spite of monitoring voltage, current, power of each string at an end of an inverter, when some of the solar cells do not operate, it is difficult to determine whether or not the system has faults due to operation of a bypass diode.
In addition, it is particularly difficult to check inverter faults or bypass diode faults because results of the faults are similar to results of the solar module faults. Furthermore, the inverter faults or the bypass diode faults cause an increase in temperature of the solar modules, and thus, the solar modules will have great deterioration. Therefore, a method or device for determining whether or not the inverter or the bypass diode has a fault is required.
FIG. 2 is a view showing a fault diagnosis technology for solar modules disclosed in Korean Patent No. 10-0919065. Referring to FIG. 2, a solar power generating apparatus 50 includes a solar array 2 having a plurality of solar subarray 2a, 2b, 2c and 2d, and an operation unit 3 communicating with the solar array 2. The solar subarray 2a, 2b, 2c and 2d includes solar panels 1a-1, . . . , 1d-10, communication units 16a-1, . . . 16d-10, a voltage detecting unit, a controller, a power unit, and a charging unit. A solar panel communicates with an adjacent solar panel through the communication unit. When a solar panel has a fault, a prior solar panel transmits both an operation state of itself and an operation state of the faulty solar panel to a next solar panel. The voltage detecting unit operated by power of the charging unit detects a voltage value of electric energy generated by the solar cell array of a solar panel. When the detected voltage value is beyond a preset reference value range, it is determined that the solar panel has a fault, and a fault signal is transmitted to an adjacent solar panel. The fault signal is transmitted to the operation unit 3. Therefore, the solar power generating apparatus 50 may simply check the faulty solar panel without a manual checking process.
However, measuring voltage, current, and etc. for each solar panel requires excessive initial investment costs. Therefore, consumers do not prefer a photovoltaic system using the fault diagnosis technology, and thus, business value and efficiency in generating renewable energy are reduced.
In addition, a monitoring system for solar power generation is disclosed in Korean Patent No. 10-0970280. The monitoring system includes a tracking detection unit, a generated electricity amount detecting unit, a temperature detecting unit, a local controller, and a communication unit. The monitoring system determines the solar module has a tracking error when a temperature value detected by the temperature detecting unit is beyond a preset range. That is, a fault diagnosis by measuring a temperature value by the temperature detecting unit disclosed in Korean Patent No. 10-0970280 is used to detect the tracking error, etc. Therefore, the fault diagnosis is unable to detect solar cell faults, etc. As shown in FIG. 2, diagnosis of a solar cell fault is performed by detecting voltage or current that has the same problem as the technology of FIG. 2.